Powder classifier

ABSTRACT

A powder classifier having a housing, a rotary member within the housing having two sets of fins separated by a conical member and means for supplying powder to be classified into the bottom of said rotor whereby certain particles will be carried upwardly through the rotor and exhausted while other particles will fall downwardly into a suitable hopper.

United States Patent Hosokawa et al.

[5 1 POWDER CLASSIFIER [72] Inventors: Masuo Hosokawa; Tohei Yokoyama;

Fumlo Nakagawa, all of Osaka, Japan 7 3 Assignee: Hosokawa FuntaikogakuKenkyusho,

Osaka, Japan [22] Filed: Aug. 5, 1970 [2]] Appl. No.2 61,223

(52] 0.5.0. ..2o9/1a9 A,'209/144,20 9/148 511 lm. Cl ..B07b 7/083 [58}Field of Search ..209/13s,139,144,14s,14s

[56] References Cited- UNITED STATES PATENTS 1,367,636 2/1921 Sturtevant..209/l39A [451 June 20, 1972 3,040,888 6/1962 Hosokawa etal ..209/ 1447 3,371,782 3/1968 Meyer et a1 ..209/l44 Primary Examiner-Frank W.Lutter Assistant Examiner-Ralph J. Hill AttomeyEugene E; Geofirey, Jr.

[ ABSTRACT A powder classifier having a housing, a rotary member withinthe housing having two sets of fins separated by a conical member andmeans for supplying powderto be classified into the bottom of said rotorwhereby certain particles will be carried upwardly through the rotor andexhausted while other particles will fall downwardly into a suitablehopper.

4 Claims, 2 Drawing Figures POWDER CLASSIFIER This invention relates toa powder classifier and more particularly to a novel and improved powderclassifier utilizing air for effecting the separation of particles ofdifi'erent sizes and for the separation of particles of differentdensities wherein the particles of the powdered material may besubstantially uniform in size. v

Prior known classifiers have not been found satisfactory because ofrelatively low classifying efficiency. With such devices the powderedmaterial was insufi'rciently dispersed and did not exist as individualparticles in the air flow. Accordingly, it was diificult toimpartuniform speed of rotation to all particlesand furthermore the air flowwas disturbed by secondary flows such as turbulence which preventedproper particle operation.

One object of the invention resides in the provision of a novel andimproved powder classifier which will effectively disperse the particlesand impart uniform rotation and steady flow to all of the particles andthus effectively and efficiently separate particles of different size ordensity as the case may be According to the invention the powderclassifier is provided with an outer housing and a classifying rotordisposed within the housing. The classifying rotor includes a diskmember having a central inlet portfor powder and air, a conical membercoaxially aligned with the disk and having its base facing the diskmember, a first group of rotating fins radially disposed between thedisk member and the base of the conical member and a second group offins radially disposed about and extending upwardly from the conicalmember. The air containing the powdered material enters the inlet portof therotating disk member, passes between the first group of radiallydisposed fins and outwardly into the housing where it then enters therotor by passing the second group of rotating fins and is then exhaustedthrough an axially disposed rotor opening. During this operation theparticles are classified and separated with the fine particles beingexhausted with the air upwardly through the rotor opening while thecoarse particles will fall and be discharged from the bottom of thehousing. In operation the classifying rotor in accordance with theinvention imparts rotating motion to the air containing the powderedmaterial with the. result that a centrifugal force is imparted to theparticles in accordance with the size or density of each of theparticles. The interaction of this centrifugal force and the aerodynamicresistance of the air flow causes the particles to be separated into twogroupsas for instance coarse and fine particles size and particleshaving large and small density.

The above and other objects of the invention will become more apparentfrom the following description and accompanying drawings forming part ofthis application.

In the drawings:

FIG. 1 is a vertical cross-sectional view of one embodiment of a powderclassifier in accordance with the invention; and

FIG. 2 is a cross-sectional view of FIG. 1 taken along the line II-Ilthereof.

The powder classifier in accordance with the invention includes acylindrical housing and a classifying rotor generally denoted by thenumeral 20. The rotor is coaxially disposed within the housing and isrotated by a drive shaft 21 the upper end being connected to suitablemeans not shown for effecting rotation of the shaft. The rotor 20includes a frustoconical member 22 fixed to the shaft 21, a lower diskmember 24 having a central inlet port 25 and an upper ring member 26. Aswill be observed more clearly in FIG. 2, a plurality of radiallydisposed fins 27 are carried between the conical surface of thefrustoconical member 22 and the upper ring member 26. A plurality ofradial fins 28 are disposed between the base of the frustoconical member22 and the lower disk member 24. An inverted cone 23 is concentricallyfixed to the underside of the base of the frustoconical member 22, thelatter being shown as a hollow body through it may of course be fonrledof a solid material in order to provide a fly-wheel effect. The space 12between the rotor and the cylindrical housing 10 serves as theclassifying cavity.

An inverted conical member 14 is disposed within the housing 10 andimmediately below the rotor 20 and the upper edges of the conical memberare fixed to the inner wall of the housing 10. This conical member formsthe lower classifying means as will be described. 7

The lower portions 18 of the housing 10 forms a hopper for removal ofthe coarse particles. An air inlet pipe 16 connects with the housing 10at a point adjoining the lower edge of the inverted conical member 14.As will be observed in FIG. 2, the inlet 16 extends tangentially fromthe housing 10 which imparts a circular motion to the air entering thehousing 10. The top of the housing 10 has a cover 30 which includes anoutlet port 32, the latter being connected to a suitable particlecollector not shown which may comprise a cyclone or bag filter and anexhaust fan. A feeder pipe 34 enters the bottom of the housing 10 and isdisposed coaxially with the rotor 20. The air and powdered materialflows through the feeder pipe and upwardly into the rotor 20. Tofacilitate an explanation of the operation of the structure as describedabove, the solid arrows indicate the flow of air while the dotted arrowsindicate the flow paths of the powdered material. Though the solidarrows are shown on one side of the structure and the dotted arrows onthe other side of the structure, this procedure has been followed forpurposes of simplification and in practice it is to be understood thatthe paths of both the air and the particles are intermixed.

The rotor is driven at a predetermined speed by means of the shaft 21and air is exhausted through the'outlet 32 at a preselected rate by anexhaust fan not shown connected to the outlet port 32. The rate of flowis also controlled by the air flow provided by the inlet pipe 16;Powdered material to be classified is carried by air flowing through thepipe 34 and fed into the inlet port of the rotor 20. The air and thepowder are directed horizontally by the guide cone 23 and then passesoutwardly between the fins 28 and impinges upon the inner wall of thehousing 10. When the powder strikes the inner wall, groups of particlesof the powder will be effectively,

broken up. Thus during this portion of the operation, the powderedmaterial is effectively separated into discrete particles.

The separated particles then flow upwardly by reason of the revolvingair flow and of the large or heavy particles falling downwardly throughthe inverted cones 14 by reason of the cavity. There is a tendency forthese heavier particles to again enter the rotor 20, but only thesmaller or lighter particles will enter the rotor and be carriedupwardly to the outlet port 22. Some of the large and heavy particlesreceive substantial centrifugal force imparted by the rotor 20 and thusovercome the sucking force of the exhaust fan. These particles settle onthe wall of the housing and then fall downwardly in the hopper l8.

i The coarse particles which fall downwardly through the inverted conel4 encounter a second flow of air provided by the pipe 16 which servesas a secondary separating function. At this point the lighter or smallerparticles which may be carried by the heavier or coarser particles willagain be blown upwardly into the space between the rotor and thehousing, and they are ultimately exhausted through the outlet 22. Thusonly the purely coarse particles will fall in the hopper l8 and may beremoved by any suitable means.

The conical surface of the frustoconical member serves as a so-calledrectifying function in that it prevents eddy currents and turbulencenear the lower portion of the radial fins 27 and thus causes the air toflow smoothly in an upward direction. A

similar function is obtained by the guide cone 23.

With the invention as described above, the powdered material iseffectively separated into discrete particles and is repeatedly andcyclically processed in two stages, one being in the rotor 20 and theother being in the inverted cone 14. Thus the particles are separatedwith a high degree of accuracy and efficiency. This is particularly thecase when separating coarse and fine particles. For example, whenpowdered heavy calcium carbonate is classified by apparatus inaccordance with the invention and it is desired to separate particlesgreater than 25 microns from particles smaller than 25 microns, thepercentage of particles smaller than 25 microns remaining with thecoarse particles is less than 5 percent by weight and the.New-

tonian classification efficiency is as high as 85 percent.

The foregoing embodiment of the invention has been shown and describedfor illustrative purposes and various modifications and changes can bemade without departing from the spirit and scope of the invention. Forexample, the radial fins 27 and 28 may be inclined with respect to theradii of the rotor 20 or may be curved. In addition, the 'speed orrotation or rotor 20 and the flow rate of the air flow and the contentof the powder in the air can be selected in accordance with the particlesize to be classified in order to obtain optimum classifying efficiency.

What is claimed is:

l. A powder classifier comprising a substantially upright cylindricalhousing having a fines outlet in the top thereof and a coarse outlet inthe bottom thereof, a classifying rotor having a rotating disk memberand an inlet port in the center, a rotating conical memberarrangedcoaxially with said disk member and having a base plane facing said diskmember, a

first group of rotating fins radially arranged between 'said disk memberandthe base plane of said'conical'member and a second group of rotatingfins radially arranged on the conical surface of said conical membersaid second group of rotating fins radiating from and defining a centralspace in direct comwall of said housing.

4. A powder classifier, in accordance with claim 1 wherein saidcylindrical housing is provided with an air inlet port extendinghorizontally and tangentially from said housing.

. ll 4 I

1. A powder classifier comprising a substantially upright cylindricalhousing having a fines outlet in the top thereof and a coarse outlet inthe bottom thereof, a classifying rotor having a rotating disk memberand an inlet port in the center, a rotating conical member arrangedcoaxially with said disk member and having a base plane facing said diskmember, a first group of rotating fins radially arranged between saiddisk member and the base plane of said conical member and a second groupof rotating fins radially arranged on the conical surface of saidconical member said second group of rotating fins radiating from anddefining a central space in direct communication with said fines outlet,and means for feeding air and powder to be classified into said inletport of said rotating disk member.
 2. A powder classifier, in accordancewith claim 1, including an inverted conical guide member concentricallyfixed to the base plane of said control member.
 3. A powder classifier,in accordance with claim 1 wherein said cylindrical housing is providedwith an annular inverted frustoconical member extending downwardly fromthe inner wall of said housing.
 4. A powder classifier, in accordancewith claim 1 wherein said cylindrical housing is provided with an airinlet port extending horizontally and tangentially from said housing.